1. Field of Invention
The present invention relates to a wind generator, and more particularly to a vertical axis wind generator structure.
2. Related Art
A wind generator generates electric energy by driving a windmill to be rotated with the wind and driving the generator via the windmill. Depending on the relationship between the rotation axis of the windmill and the wind direction, the wind generator can further be classified as a horizontal axis wind generator in which the rotation axis of the windmill is horizontal with respect to the wind direction and a vertical axis wind generator in which the rotation axis of the windmill is vertical with respect to the wind direction. Horizontal axis wind generators are usually applied as large scale wind generators arranged in an open filed while vertical axis wind generators are usually applied as small scale wind generators arranged on top of large buildings.
In recent years, issues such as energy saving and environment protection have drawn considerable attention, which makes the demand for small scale wind generators increase. Arranging wind generators on top of large buildings can supply part of the electricity to public facilities in the building so as to achieve energy saving. However, several problems exist in small scale wind generators, for example, they are arranged on top of buildings, ambient temperature may vary, the wind generator mechanism has a poor endurance, the bearing has a poor lubrication, and the structure strength cannot be reinforced according to the install location. All of such problems have impacts on the lifespan of small scale wind generators, so that small scale wind generators have a high cost of implementation, which is unacceptable for proprietor of the buildings.
The Taiwan patent publication No. 168238 disclosed a vertical axis wind turbine blade construction and US patent publication No. 2007102938 disclosed a vertical wind turbine power generation system. In the two patents just mentioned, in order to enable the wind blade to be rotated smoothly, a fixed bearing, such as ball bearing or thrust bearing, is disposed between the rotation axis and the stationary shaft of the wind blade. The bearing is used for decreasing the frictional resistance in the rotation movement and thus has a direct impact on the rotation and lifespan of the wind blade.
Depending on the practical operation conditions of the wind generator, the direction of the air flow driving the wind blade to be rotated is not fixed. Particularly, if the wind generator is arranged on top of a building, the air flow comes from all directions, such as a lateral air flow, upward air flow, or downward air flow, the ball bearing or thrust bearing conventionally used between the rotation axis and the stationary shaft cannot withstand the forces from all the directions. Furthermore, the temperature resulting from the rotation movement of the rotation axis or the ambient temperature would also impact the lifespan of the bearing. The variations in the operation or the environment cannot be overcome simply by decreasing the frictional resistance via the bearing. Further, if the bearing breaks down, it is not easy to repair or replace the wind generator arranged on top of a building, thus leading to an increased maintenance cost.